1. Technical Field
The present invention relates to a plasma processing apparatus that processes a substrate by using plasma, and a plasma processing method thereof.
2. Description of the Related Art
As examples of a plasma processing apparatus, two types of plasma processing apparatuses that perform ion implantation using plasma are known.
Type 1: The application of a bias voltage is performed by using a high-frequency AC in order to reduce the influence of a resist pattern or the like on a substrate (refer to the pamphlet of WO2006/107044).
Type 2: The application of a positive bias voltage is performed by using a pulse power source (refer to Japanese Unexamined Patent Publication No. 2001-358129).
The type 1 is often used when the bias voltage is low. However, since AC voltage is applied, extra energy is implanted to the wafer, and the thermal load on the wafer increases.
The type 2 can adjust a positive potential not involved with ion implantation, and decrease the thermal load on the wafer.
However, although the ion implantation apparatus includes an electrostatic chuck (which may be hereinafter simply referred to as an ESC) that holds a substrate inside a vacuum container and performs temperature management of the substrate, the bias application method differs according to the type of the ESC. That is, examples of the ESC include a CR type (Coulomb type) that capacitively prevents current from flowing and a JR type (Johnsen-Rahbek type) that makes minute current flow.
When the CR type ESC is used, the current for ion implantation flows as a capacitance component without being influenced by substrate resistance due to upper and lower capacitors. On the other hand, when the JR type ESC is used, the current for ion implantation is influenced by a substrate resistance. However, when the substrate has a resist mask (a resist pattern) or the like that prevents the current from flowing, the current flows in the peripheral direction of the substrate through the position contacting the ESC, whereby the uniformity of the ion implantation is influenced. In general, the method of using the CR type ESC is rarely influenced by the resist mask or the like, and uniformity of the ion implantation can be stably obtained.
As for the bias application of the ion implantation apparatus that uses a pulse power source and is used to perform ion implantation, there are three types of parameter, that is, frequency, duty ratio, and voltage. However, such parameters are not particularly optimized in the current state, and in fact, desirable parameter values are determined through a test. For this reason, this method is not efficient.
When ion implantation is performed by using a pulse power source, the JR type ESC is used in many cases. This is because DC current does not easily flow in the CR type ESC. In this case, the frequency of the pulse power source is set to 10 kHz or less. As the upper limit of the frequency, the frequency (about 1 MHz or less) at which ions can be traced is set as the upper limit. However, even in the JR type ESC, the current of the capacitance component of the capacitor is mainly used at a high frequency (10 kHz or more).